1. Field of the Invention
The present invention relates to an image forming apparatus having a recording head in which multiple nozzles for ejecting liquid droplets and an actuator for causing the liquid droplets to be ejected from the multiple nozzles are formed and forming an image by causing the liquid droplets to be ejected from the multiple nozzles based on image data, and to an image forming method using a recording head in which multiple nozzles for ejecting liquid droplets and an actuator for causing the liquid droplets to be ejected from the multiple nozzles are formed and forming an image by causing the liquid droplets to be ejected from the multiple nozzles based on image data.
2. Description of the Related Art
Inkjet recording apparatuses have recording heads for respective colors mounted on a carriage. Multiple nozzles for ejecting ink are formed in the recording heads. The recording apparatuses form images by ejecting ink while causing the carriage to perform scanning in directions perpendicular to a direction in which a recording medium is conveyed. In the case of forming images in the recording apparatuses, head driving signals and control data for causing actuator parts to form an image are transferred from a control part on the apparatus body side to drivers on the recording head side. A common transfer system is serial data transfer. The head driving signals are signals to drive the actuator parts provided in the recording heads.
The control data transferred to the recording heads include image data and head driving signal masking signals. The image data determine kinds of ink droplets ejected from the respective nozzles. The head driving signal masking signals mask the head driving signals to generate driving waveforms for causing the recording heads of the respective colors to eject ink liquid droplets corresponding to the kinds of ink droplets.
Japanese Laid-Open Patent Application No. 2009-286112 describes an image forming apparatus that transfers data from a control part on the body side to recording heads.
A description is given, with reference to FIG. 1 through FIG. 4, of the image forming apparatus described in Japanese Laid-Open Patent Application No. 2009-286112.
FIG. 1 is a diagram illustrating an image forming apparatus that causes data to be transferred from a control part to recording heads.
Referring to FIG. 1, an image forming apparatus 10 includes a control part 11 provided on the apparatus body side and multiple recording heads 13 provided in a carriage 12.
In the image forming apparatus 10, firmware that controls hardware is contained in a read-only memory (ROM) 14. According to the image forming apparatus 10, in response to reception of a print job (image data) from a host personal computer (host PC) 20, a central processing unit (CPU) 21 causes the image data to be stored in a random access memory (RAM) 15, and causes a main scanning control part 16 to move the carriage 12 to a position above a recording medium. A recording head control part 30 transfers data including the image data contained in the RAM 15 to recording head driving parts 40 in conjunction with the position information of the carriage received from a main scanning encoder 17. The recording head driving parts 40 drive the recording heads 13 based on the data transferred from the recording head control part 30 to cause the recording heads 13 to eject ink droplets.
FIG. 2 is a diagram for illustrating data transfer from a recording head control part to a recording head driving part. The recording head driving part 30 generates a head driving signal (hereinafter, a common driving signal) Vcom, and outputs the common driving signal Vcom to the recording head driving part 40. In the case of FIG. 1, common driving signals from the recording head control part 30 to the respective recording head driving parts 40 may also be collectively referred to as “common driving signal Vcom.” The recording head control part 30 transfers data including image data and a head driving waveform masking signal to mask the common driving signal Vcom to the recording head driving part 40.
The recording head control part 30 transfers image data corresponding to an image to be printed to a shift register 42 of the recording head driving part 40 with a transfer clock signal SCK of serial data SD1 and SD0 (hereinafter indicated as SD[1:0]). A latch part 43 of the recording head driving part 40 latches each register value of the shift register 42.
Further, the recording head control part 30 transfers mask pattern transfer data MD in serial data to a mask pattern shift register 46 of the recording head driving part 40 with a mask pattern transfer clock signal MCK. Further, the recording head control part 30 transfers a mask pattern transfer data latch signal MLn to a mask pattern latching part 47.
The mask pattern latching part 47 latches the mask pattern transfer data MD captured into the mask pattern shift register 46 with the mask pattern transfer data latch signal MLn, and switches head driving mask patterns MN[7:0] (head driving mask patterns MN0 through MN7) and outputs the head driving mask patterns MN[7:0] to a decoder 44. At this point, the timing of switching of the mask pattern is controlled by the operational timing of the mask pattern transfer data latch signal MLn.
The decoder 44 decodes and outputs the image data SD[1:0] and the head driving mask patterns MN[7:0]. A level shifter 45 shifts (converts) the level of a logic level voltage signal that is the output of the decoder 44 to a level that allows the operation of an analog switch 41. The analog switch 41 is turned ON/OFF (opened/closed) based on the output of the decoder 44 provided via the level shifter 45.
FIG. 3 is a diagram illustrating the mask pattern latching part 47. The mask pattern latching part 47 includes flip-flop circuits and multiplexers, which form a latch circuit. The mask pattern latching part 47 latches data in the mask pattern shift register 46 if the mask pattern transfer data latch signal MLn is LOW in level (hereinafter L-level) and the mask pattern transfer data MD is L-level, and if the mask pattern transfer data latch signal MLn is L-level and the mask pattern transfer data MD is high in level (hereinafter, H-level), all of the head driving mask patterns MN[7:0] are reset to H-level.
FIG. 4 illustrates a truth table of mask pattern serial transfer signals. The mask pattern latching part 47 determines whether to latch or reset data in the mask pattern shift register 46 based on the state of the mask pattern transfer data at the time when the mask pattern latching part 47 enters a latching state in response to the mask pattern transfer data latch signal MLn becoming L-level. If the mask pattern latching part 47 determines that the data in the mask pattern shift register 46 is to be reset, the mask pattern latching part 47 sets all of the head driving mask patterns MN[7:0] (mask pattern signals) to H-level (ALL-H), thereby resetting the data in the mask pattern shift register 46.